Facsimile printing blade assembly

ABSTRACT

An improved printing blade apparatus for a facsimile printer which uses a rotating band type blade. The apparatus comprises a pair of capstan rollers for holding the blade inclined to the paper path, and a pair of skewed rollers for urging the upper blade edge toward a registration stop. A leaf spring contacts the blade immediately below its upper edge to bias it towards the paper.

United States Patent Kunio A. Sumida Los Angeles, Calif.

[21] Appl. No, 753,254

[22] Filed Aug. 16,1968

[45] Patented Mar. 9, 1971 [73] Assignee Telautograph Corporation Los Angeles, Calif.

[72] Inventor [54] FACSIMILE PRINTING BLADE ASSEMBLY 8 Claims, 5 Drawing Figs.

[52] US. Cl 346/139, 346/ 101 [51] Int. Cl 601d 15/24 [50] Field ofSearch 346/101, 139, 74, 74 (E); 178/66 [56] References Cited UNITED STATES PATENTS 2,515,864 7/1950 Finch et a1. 346/101 2,758,906 8/1956 Alden 34 6/74 2,910,666 10/1959 Hardgrove et a1. 346/101X 3,389,218 6/1968 Balamuth et al. l78/6.6 2,621,999 12/1952 Alden 346/74 2,743,990 5/1956 Leonard 346/101 2,776,183 l/l957 Alden 346/101 Primary Examiner-Joseph W. l-lartary Attorneys-Arthur Freilich and Samuel Lindenberg ABSTRACT: An improved printing blade apparatus for a facsimile printer which uses a rotating band type blade. The apparatus comprises a pair of capstan rollers for holding the blade inclined to the paper path, and a pair of skewed rollers for urging the upper blade edge toward a registration stop. A leaf spring contacts the blade immediately below its upper edge to bias it towards the paper.

PATENTEU MAR 9 I97! SHEET 2 OF 2 I INVENTOR.

RUM/o A Sum/ ,4

IFACSIMIILE PRINTING BLADE ASSEMBLY BACKGROUND OF THE INVENTION A 1. Field of the Invention This invention relates to facsimile type printers.

2. Description of the Prior Art The most common type of facsimile printer marks an electrolytic paper by positioning a pair of electrodes on either side of the paper. In one such printer, one electrode comprises a wire wound as a helix around a drum, while the other comprises a thin blade extending across the width of the paper and spring biased toward it. As the drum turns, the contact point at which the paper is pressed between the wire and blade electrodes moves along a line across the paper. The paper advances slowly, so that successive lines cover the entire paper surface. Current applied between the electrodes causes iron, silver, or other ions in the blade to enter the electrolyte of the paper, to darken it and thereby form an image. The spot at which the printing blade contacts the paper is generally of somewhat square shape with sides of about one-hundredth inch to achieve high resolution. The speed at which the drum rotates is typically on the order of 1,000 revolutions per minute to achieve a printing speed of about inches per minute.

The printing blade is electrolytically worn away or eroded by the printing process, and the presence of long vertical black lines on the copy can result in the formation of deep grooves in the blade, which tear the paper. One way of preventing the formation of grooves is by forming the blade as a continuous loop band that rotates. The band-formed blade is positioned so that its edge contacts the paper, and it is spring biased toward the paper.

Several problems arise in the use of looped band blades. One problem is achieving high blade compliance. High compliance is necessary because the helical wire may move toward and away from the paper by several thousandths inch during a drum rotation. This is a result of the fact that the radial distance from the axis of the rotating drum to different parts of the wire helix wound thereon mayvary by several thousandths inch. A simple stationary blade is generally constructed to be of light weight, and it can be readily biased toward the drum to achieve high compliance. However, the looped band blade cannot be readily dissociated from the rollers that hold it. Yet, if the rollers and blade are biased as a single unit toward the paper, then the large mass of this unit prevents the realization of the high compliance necessary for good printing with a high speed drum rotation.

OBJECTS AND SUMMARY OF THE INVENTION One object of the present invention is to provide an improved printing blade assembly for facsimile printers.

Another object is to provide means for the more compliant support of a band type facsimile printer blade.

In accordance with the present invention, printing blade apparatus is provided for a facsimile type printer, which enables high speed printing with long blade life. The apparatus comprises a printing blade in the form of a looped hand, one side of the loop extending across the width of the recording paper to provide a printing edge in contact with the paper. However, instead of being oriented perpendicular to the paper, the blade is inclined from the perpendicular at an angle such as 60 and therefore is inclined from the paper path by an angle such as 30. Aleaf spring presses the band toward the paper, to assure contact of the printing edge with the paper.

The band printing blade is held between a pair of rollers, one of which serves as a drive or capstan roller which is rotated to drive the band. A pair of skew idler rollers contact the band to urge the printing edge thereof toward a registration stop. This fixes the position of the printing edge of the blade so it does not wander up and down.

The novel features of the invention are set forth with particularity in the appended claims. The invention will be best understood from the following description when read in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partial perspective view of a facsimile type printer constructed in accordance with the invention;

FIG. 2 is a sectional side elevation view of the apparatus of FIG. I;

FIG. 3 is an enlarged sectional view of the area 3-3 of FIG. 2;

FIG. 4 is a more detailed elevation view of the blade support apparatus, taken on the line 4-4 of FIG. I; and

FIG. 5 is a side elevation view of the 'blade support apparatus of FIG. 4.

DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1, the printer comprises a bracket 10 for holding a roll of electrolytic recording paper shown in phantom lines 12. The paper or other suitable web extends along a web path between two electrodes, one in the form of a wire 14 and the other in the fonn of a band 16. The printing blade or band 16 is angled so that only an edge thereof contacts the paper. The wire 14 is wound as a one-turn helix on a drum 18 that is rotated at high speed. The helix wire contacts a supported area of the paper at a point that sweeps once across the width of the paper for each revolution of the drum. An electrical current is passed through the paper between the band and the wire electrodes, by means of electrical contacts (not shown) on the band and wire. The current causes iron or other ions in the band 16 to move into the electrolytically impregnated paper and darken it. The amount of current can be varied to vary the darkening.

The paper 12 is pulled slowly along its path by a paper drive (not shown), while the rotating drum 18 causes successive lines to be printed on the paper. The area at which the wire 14- contacts the paper is typically a square with sides about 0.0l0 inch long, so each line of printing is one-hundredth inch wide. The drum typically rotates at a speed on the order of 1,000 revolutions per minute, so that 1,000 lines, which cover a 10 inch length of paper, are printed each minute.

The manufacture of the drum l8 and the placement of the wire 14 thereon are closely controlled so that the outer edge of the wire is at an almost constant radius from the rotational axis 20 of the drum. However, it is difficult to maintain a tolerance of less than several thousandths inch. In order to maintain the paper tightly pressed between the wire 14 and edge of the band 16, the band must have a high compliance. That is, the portion of the band opposite the point where the wire 14 contacts the paper must readily move in and out by several thousandths inch to constantly press against the paper.

A relatively high pressing force such as I75 grams must be exerted for a printing spot or contact area of about 0.01' inch square to maintain control of darkness, but the pressure must not be too high or else the paper will tear. The difficulty of achieving the required compliance is a major factor in limiting the speed of rotation of the drum l8 and therefore the printing speed capability of the printer.

In accordance with the present invention, high compliance of the band printing blade 16 is achieved by orienting the blade so it is inclined by less than to the plane of the paper 12 instead of being perpendicular to it. That is, the side of the loop nearest the web path, is a planar blade portion inclined by less than 90 to the path. As shown more clearly in FIG. 3, the blade 16 in this embodiment of the invention is at an angle A of 30 from a line 22 that is parallel to the web path. The printing edge 30 is worn to a level with respect to the plane of the blade, which results in the edge being parallel to the web path. A leaf backup spring 24 is provided which presses the side of the blade toward the paper. As will be explained below in greater detail, the spring presses the printing blade so that only a small area of the blade moves toward and away from the paper, independently of the rest of the blade and its supporting apparatus. The small mass of such a blade portion allows it to move rapidly to thereby achieve high compliance.

The band printing blade is held taut between two rollers, one being an idler roller 26 and the other being a drive capstan 28. The drive capstan 28 is rotated at a slow speed such as two revolutions per minute to constantly rotate the band printing lers 36 and 38 which urge the blade upward toward the stops.

The upward bias of the blade, which is realized in this embodiment of the invention by the skew rollers 36 and 38, must be low enough to prevent rollover of the blade at the printing edge. If the blade edge is rolled back, slivers are continually removed from the blade by the stops, and blade life is shortened considerably. If the blade edge is rolled forward, the copy will appear to be scratched. The bias must be especially low in the case of blades made of soft material such as silver.

One method which has been tried for achieving the required bias is to taper the two rollers 26 and 28 which hold the blade taut, to urge the blade up toward stops or toward shoulders on the rollers. However, it was found that a small taper was required, which provided a smallest roller diameter only several thousandths inch less than the largest, and that the amount of taper was critical. A slightly greater taper resulted in too high a bias and rolled over edges. A smaller taper, or a lack of precision in aligning the rollers to turn parallel to each other, resulted in up and down wandering of the blade. Furthermore, the tapered rollers had to be made of a hard material to maintain accuracy of taper. Such hardness resulted in the necessity forv high blade tension to prevent slippage of the blade on the drive roller as it pulled the blade past the backup spring. I-ligh tension is detrimental since it adds to blade stress. This stress can considerably shorten blade life when combined with the weakening effect resulting from blade corrosion by the electrolyte of the paper. The use of the skew rollers, to be described in greater detail below, substantially reduces the severity of these conditions.

As shown in greater detail in FIGS. 4 and 5, the printing blade assembly comprises a frame 41 which includes a main frame portion 43 and a secondary frame portion 45. The main frame portion supports one main roller 28, skew roller 38, and stop 34, while the secondary frame portion supports the other corresponding components. The main frame portion is supported on a cover of the printer housing, in a manner to be described.

The skew rollers 36 and 38, which assure printing edge registration, are idler rollers which are positioned just in front of the stops 32 and 34 (with respect to the direction of blade rotation). The skew rollers are tapered, with their smaller diameters at the top where the stops 32 and 34 are located. In addition, the skew rollers are rotatably mounted on shafts 40 and 42 which are inclined from the shafts 44 and 46 on which the main rollers 26 and 28 are mounted.

The taper and incline are provided to urge the blade upward toward the stops. The blade does not follow the steep upward path at the skew rollers, but slips on these rollers. The upward bias depends to a great extent upon the pressure of the skew rollers on the blade. This pressure is held to a relatively low value which is sufficient to provide the desired amount of upward blade bias. The skew rollers can be either tapered or inclined, instead of both, to result in the skew roller surfaces in contact with the blade moving witha component toward the stops.

The use of skew rollers to maintain blade registration enables the employment of the main rollers 26 and 28 solely to keep a certain minimum tension and to drive the blade around its loop configuration. The roller 28 serves as a drive capstan, its shaft 46 having a coupling end 52 which is coupled to a gear head motor (not shown) for slow rotation. The surface of the roller 28 need not be maintained in a cylindrical shape with high accuracy. Accordingly, the roller is constructed with a sleeve 29 of elastomeric material on an inner core 31, the sleeve having a high coefficient of friction with the metal of the printing blade. A relatively low blade tension such as 5 pounds is therefore sufficient to prevent slippage of the roller 28. This reduces stress on the blade and increases its life.

Blade tension is maintained by a spring 54 disposed about a plunger 55, which biases the main and secondary frame portions away from each other, to thereby bias apart the main rollers 26 and 28. The spring is preloaded to exert the desired force such as I0 pounds. The frame portions are slideably coupled together, and are maintained in alignment by pins 56 and 58 on the main frame portion that engage slots 60 and 62 in the secondary frame portion. A pair of holes 64 and 66 in the main ,frame portion receive bolts that attach to support mounts that support the frame on the cover of the printer housing.

As shown in FIGS. 1 and 2, the backup printer blade spring 24 has an almost L cross section, with the base 68 having a pair of slots 70 and 72. A pair of screws 73 extend through the slots and through corresponding holes 75 in the main frame portion to hold the spring to the frame. The backup spring 24 is held at an angle B of about 10 with the printing blade 16. This allows all but the outer end 24C of the spring to be spaced away from the printing blade 16. This spacing is desirable because vapor residue from the electrolytic paper collects along the blade. If the springl24 were placed flat against the blade, the vapor residue would cause binding, and require more blade tension to drive it around the loop.

The position of the outer spring portion 24C which contacts the printing blade is an important factor in good printer operation. If the distance D between the outer end of the backup spring and the printing edge 30 is too great, this portion of the blade loses stiffness and the helix wire 14 indents considerably into it. Because of the small diameter E of the helix wire, this introduces high stress at the blade printing edge. The result is formation of minute cracks and chipping, which prevents clean printing and reduces blade life. Reduction of this distance D increases the stiffness of this area and prevents these harmful results. It has been found that the" distance D generally should not exceed 22 times the thickness T of the blade. In particular, it has been found that for a stainless steel blade with a thickness Tof 0.004 inches, and a helix wire with a diameter E of 0.032 inches, which are typical values, the distance D must not exceed 0.090 inches to prevent the foregoing harmful effects.

The frame 41 on which the rollers and backup spring are carried, is supported by a pair of laterally spaced spring support assemblies 74, one of which is shown in detail in FIG. 2. Each support assembly includes a mount 76 held by a heavy stiff spring 78 that is fastened to the cover of the printer housing. A pair of screws 79 extend through holes (shown at 64 and 66 in FIG. 5) in the main frame portion to hold the frame on the mount 76. A pair of laterally spaced adjusting screws 80 and 82 (also shown in FIG. 1) enable small adjustments to be made in the position of the frame. The adjusting screw 80 has a conical end 84 that presses between the mount 76 and a portion 86 of the printer housing. Tightening of the screw 80 pushes the mount 76 toward the helix wire to move the printing blade assembly toward the paper path. The other adjusting screw is mounted in the same manner. Each of the still springs 78 can be twisted slightly, so either end of the printing assembly can be moved closer or further from the paper path independently of the other end. By adjusting the screws 80 and 82, a uniform printing blade pressure can be achieved across the entire width of the paper path.

The angle A between the printing blade 16 and the path of the recording paper shown at 22, which is shown as 30 in the figures, can vary within a wide range. However, it is preferably maintained between 7 and 70 At a small angle of less than about 7 the printing edge 30 becomes more than about 10 times as wide as the thickness T of the blade. This results in a very large printing spot for the usual blade thickness, and in a wide variation in printing spot size for small changes in angle.

At large angles of more than about 70 only a small component of the backup spring bias' is towards the web path, and

blade biasing becomes difficult.- I

A printer constructed in accordance with this invention has' been described and illustrated herein, it is recognized that modifications and variations may readily occur to those skilled in the art, and, consequently, it is intended that the claims be interpreted to cover such modifications and equivalents.

I claim:

1. Printing blade apparatus for receiving a printing blade to print on a recording medium which moves along a path comprising:

a pair of rollers disposed at either side of said path, with their axes substantially parallel to each other and inclined toward said path, for holding a band-formed printing blade in a loop with one edge adjacent to said path; and

skew roller means positioned to bear against a blade which is looped about said pair of rollers, to urge said blade toward said web path.

2'. A printer comprising:

a housing;

means defining a web path;

a frame mounted on one side of said path;

a band of metal formed as a continuous loop;

. a pair of rollers for holding said band with one side extending across said web path, and at an'angle on the order of 30 with said path;

means for rotating one of said rollers to drive said band;

a stop mounted on said frame to register the edge of said band which is closest to said web path;

a skew roller mounted on said frame and engaged with said band to urge it toward said stop; and

a leaf spring having an outer portion engaged with said band substantially along a line parallel to and spaced a predetermined distance from the edge of said blade which is closest to said web path.

3. The printer described in claim 2 wherein said predetermined distance is no greater than approximately 0.09 inch.

4. Printing blade apparatus for use in a printer that prints on a web that moves along a web path comprising:

a flexible blade in the form of a continuous band, having a blade portion with an edge extending across said path,

. said blade portion inclined by less than 90 to said path; spring means disposed against a side of said blade portion opposite said path for biasing said blade portion toward said path;

a pair of rollers for holding said blade taut;

means for driving one of said rollers to rotate said blade;

a registration stop for limiting the movement of said edge of said blade toward said path, to a predetermined registration position; and

skew roller means having a rotatable surface engaged with said blade, said rotatable surface being skewed to move with a component directed toward the registration position of said blade edge.

5. Printing blade apparatus for printing on a recording medium which moves along a path comprising:

a pair of rollers disposed at either side of said path, with their axes substantially parallel to each other and inclined toward said path; a band-formed printing blade extending in a loop around said pair of rollers, said blade having a printing edge with a portion adjacent to said web path; skew rollermeans positioned to bear against said blade, to

urge it toward said web path; and a leaf spring having a first portion disposed against said blade substantially along a linear area adjacent to said printing edge and having a second portion extendin away from said first portion at an angle of at least severa degrees away from the plane of said blade.

6. Printing blade apparatus for printing on a recording mediumwhich moves along a path comprising:

a pair of rollers disposed at either side of said path, with their axes substantially parallel to each other and inclined toward said path;

a printing blade in the form of a thin flexible band extending around said pair of rollers, and having a blade edge which extends substantially across said web path; and

skew roller means positioned to bear against said blade to urge it toward said web path.

7. A printer comprising:

means defining a web path;

means disposed on one side of said path for defining a printing spot that moves across said path; and

a printing blade assembly disposed opposite said means for defining a printing spot, including a frame, a apair of rollers mounted on said frame, a printing blade substantially in the form of a band which extends around said rollers, said rollers positioned to hold one side of said band substantially in extension across said web path and at an angle therewith ranging between approximately7 and 70, stop means for abutting the edge of said band which is closest to said path, and at least one tapered roller in contact with said band for urging said band toward said stop means, said tapered roller having a narrowest diameter end nearest said edge which abuts said stop means. 8. A printer comprising: means defining a web path; means disposed on one side of said path for defining a printing spot that moves across said path; and a printing blade assembly disposed opposite said means for defining a printing spot, including a frame, a pair of rollers mounted on said frame, a printing blade substantially in the form of a band which extends around said rollers, said rollers positioned to hold one side of said band substantially in extension across said web path and at an angle therewith ranging between approximately 7 and 70 stop means for abutting the edge of said band which is closest to said path, and at least one skew roller in contact with said band, for urging said band toward said stop means, said skew roller having an axis inclined to the axis of said pair of rollers to urge said band toward said web path. 

1. Printing blade apparatus for receiving a printing blade to print on a recording medium which moves along a path comprising: a pair of rollers disposed at either side of said path, with their axes substantially parallel to each other and inclined toward said path, for holding a band-formed printing blade in a loop with one edge adjacent to said path; and skew roller means positioned to bear against a blade which is looped about said pair of rollers, to urge said blade toward said web path.
 2. A printer comprising: a housing; means defining a web path; a frame mounted on one side of said path; a band of metal formed as a continuous loop; a pair of rollers for holding said band with one side extending across said web path, and at an angle on the order of 30* with said path; means for rotating one of said rollers to drIve said band; a stop mounted on said frame to register the edge of said band which is closest to said web path; a skew roller mounted on said frame and engaged with said band to urge it toward said stop; and a leaf spring having an outer portion engaged with said band substantially along a line parallel to and spaced a predetermined distance from the edge of said blade which is closest to said web path.
 3. The printer described in claim 2 wherein said predetermined distance is no greater than approximately 0.09 inch.
 4. Printing blade apparatus for use in a printer that prints on a web that moves along a web path comprising: a flexible blade in the form of a continuous band, having a blade portion with an edge extending across said path, said blade portion inclined by less than 90* to said path; spring means disposed against a side of said blade portion opposite said path for biasing said blade portion toward said path; a pair of rollers for holding said blade taut; means for driving one of said rollers to rotate said blade; a registration stop for limiting the movement of said edge of said blade toward said path, to a predetermined registration position; and skew roller means having a rotatable surface engaged with said blade, said rotatable surface being skewed to move with a component directed toward the registration position of said blade edge.
 5. Printing blade apparatus for printing on a recording medium which moves along a path comprising: a pair of rollers disposed at either side of said path, with their axes substantially parallel to each other and inclined toward said path; a band-formed printing blade extending in a loop around said pair of rollers, said blade having a printing edge with a portion adjacent to said web path; skew roller means positioned to bear against said blade, to urge it toward said web path; and a leaf spring having a first portion disposed against said blade substantially along a linear area adjacent to said printing edge and having a second portion extending away from said first portion at an angle of at least several degrees away from the plane of said blade.
 6. Printing blade apparatus for printing on a recording medium which moves along a path comprising: a pair of rollers disposed at either side of said path, with their axes substantially parallel to each other and inclined toward said path; a printing blade in the form of a thin flexible band extending around said pair of rollers, and having a blade edge which extends substantially across said web path; and skew roller means positioned to bear against said blade to urge it toward said web path.
 7. A printer comprising: means defining a web path; means disposed on one side of said path for defining a printing spot that moves across said path; and a printing blade assembly disposed opposite said means for defining a printing spot, including a frame, a pair of rollers mounted on said frame, a printing blade substantially in the form of a band which extends around said rollers, said rollers positioned to hold one side of said band substantially in extension across said web path and at an angle therewith ranging between approximately 7* and 70* , stop means for abutting the edge of said band which is closest to said path, and at least one tapered roller in contact with said band for urging said band toward said stop means, said tapered roller having a narrowest diameter end nearest said edge which abuts said stop means.
 8. A printer comprising: means defining a web path; means disposed on one side of said path for defining a printing spot that moves across said path; and a printing blade assembly disposed opposite said means for defining a printing spot, including a frame, a pair of rollers mounted on said frame, a printing blade substantially in the form of a band which extends around sAid rollers, said rollers positioned to hold one side of said band substantially in extension across said web path and at an angle therewith ranging between approximately 7* and 70* , stop means for abutting the edge of said band which is closest to said path, and at least one skew roller in contact with said band, for urging said band toward said stop means, said skew roller having an axis inclined to the axis of said pair of rollers to urge said band toward said web path. 